There are a number of skid steer vehicles that need to have transmissions which have the capability to provide a separate controlled speed output to each side of the vehicle in order to steer it. These include skid steer loaders, crawler tractors and loaders, tracked farm tractors, asphalt pavers and utility machines. These vehicles may have wheels or tracks, and if wheeled may have either a fixed or variable wheel geometry. Many of these vehicles have a hydrostatic transmission for each side of the vehicle with a separate speed control for each transmission in order to steer, typically referred to as a dual path transmission. These dual path transmissions must be coordinated in order to achieve both steering and forward or reverse motion control.
In order to increase the utility of these vehicles, output speeds in the forward direction of travel are increasing. As wheeled vehicles such as skid steer loaders have a short wheelbase, the need for precise control of the steer function increases as speed increases. Dual path transmissions may not provide the necessary control for these higher speed vehicles.
High efficiency of operation is also becoming more important in order to reduce operating cost. Compact size is important for ease of installation.
It is therefore a principal object of this invention to provide a hydromechanical transmission with differential steer which accommodates the need for increasing vehicle speeds with good steer control, particularly in wheeled vehicles such as skid steer loaders.
A further object of the invention is to provide a hydromechanical transmission with differential steer which satisfies the needs for high efficiency, compact size and low cost.
These and other objects will be apparent to those skilled in the art.